linux-kernel - Re: [PATCH] perf stat: Show percore counts in per CPU output

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Date:   Mon, 10 Feb 2020 15:01:20 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf stat: Show percore counts in per CPU output

On Mon, Feb 10, 2020 at 09:46:46PM +0800, Jin, Yao wrote:
> 
> 
> On 2/10/2020 9:28 PM, Jiri Olsa wrote:
> > On Thu, Feb 06, 2020 at 09:56:13AM +0800, Jin Yao wrote:
> > > We have supported the event modifier "percore" which sums up the
> > > event counts for all hardware threads in a core and show the counts
> > > per core.
> > > 
> > > For example,
> > > 
> > >   # perf stat -e cpu/event=cpu-cycles,percore/ -a -A -- sleep 1
> > > 
> > >    Performance counter stats for 'system wide':
> > > 
> > >   S0-D0-C0                395,072      cpu/event=cpu-cycles,percore/
> > >   S0-D0-C1                851,248      cpu/event=cpu-cycles,percore/
> > >   S0-D0-C2                954,226      cpu/event=cpu-cycles,percore/
> > >   S0-D0-C3              1,233,659      cpu/event=cpu-cycles,percore/
> > > 
> > > This patch provides a new option "--percore-show-thread". It is
> > > used with event modifier "percore" together to sum up the event counts
> > > for all hardware threads in a core but show the counts per hardware
> > > thread.
> > > 
> > > For example,
> > > 
> > >   # perf stat -e cpu/event=cpu-cycles,percore/ -a -A --percore-show-thread  -- sleep 1
> > > 
> > >    Performance counter stats for 'system wide':
> > > 
> > >   CPU0               2,453,061      cpu/event=cpu-cycles,percore/
> > >   CPU1               1,823,921      cpu/event=cpu-cycles,percore/
> > >   CPU2               1,383,166      cpu/event=cpu-cycles,percore/
> > >   CPU3               1,102,652      cpu/event=cpu-cycles,percore/
> > >   CPU4               2,453,061      cpu/event=cpu-cycles,percore/
> > >   CPU5               1,823,921      cpu/event=cpu-cycles,percore/
> > >   CPU6               1,383,166      cpu/event=cpu-cycles,percore/
> > >   CPU7               1,102,652      cpu/event=cpu-cycles,percore/
> > 
> > I don't understand how is this different from -A output:
> > 
> >    # ./perf stat -e cpu/event=cpu-cycles/ -A
> >    ^C
> >     Performance counter stats for 'system wide':
> > 
> >    CPU0              56,847,497      cpu/event=cpu-cycles/
> >    CPU1              75,274,384      cpu/event=cpu-cycles/
> >    CPU2              63,866,342      cpu/event=cpu-cycles/
> >    CPU3              89,559,693      cpu/event=cpu-cycles/
> >    CPU4              74,761,132      cpu/event=cpu-cycles/
> >    CPU5              76,320,191      cpu/event=cpu-cycles/
> >    CPU6              55,100,175      cpu/event=cpu-cycles/
> >    CPU7              48,472,895      cpu/event=cpu-cycles/
> > 
> >         1.074800857 seconds time elapsed
> > 
> 
> The results are different.
> 
> With --percore-show-thread, CPU0 and CPU4 have the same counts (CPU0 and
> CPU4 are siblings, e.g. 2,453,061 in my example). The value is sum of CPU0 +
> CPU4.

so it shows percore stats but displays all the cpus? what is this good for?
to see which cpus are in core? if that's the case then I think we could
somehow display the cpu numbers for core in --per-core output, like:

S0-D0-C0(0,4)                395,072      cpu/event=cpu-cycles,percore/
S0-D0-C1(1,5)                851,248      cpu/event=cpu-cycles,percore/
S0-D0-C2(2,6)                954,226      cpu/event=cpu-cycles,percore/
S0-D0-C3(3,7)              1,233,659      cpu/event=cpu-cycles,percore/


> 
> Without --percore-show-thread, CPU0 and CPU4 have their own counts.
> 
> > also the interval output is mangled:
> > 
> >    # ./perf stat -e cpu/event=cpu-cycles,percore/ -a -A --percore-show-thread  -I 1000
> >    #           time CPU                    counts unit events
> >       1.000177375      1.000177375 CPU0             138,483,540      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU1             143,159,477      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU2             177,554,642      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU3             150,974,512      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU4             138,483,540      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU5             143,159,477      cpu/event=cpu-cycles,percore/
> >       1.000177375      1.000177375 CPU6             177,554,642      cpu/event=cpu-cycles,percore/
> > 
> > jirka
> > 
> 
> Sorry, why the interval output is mangled? It's expected that CPU0 and CPU4
> have the same counts.

there are 2 timestamp columns and the header line does
not align with the data

jirka